Thailand braced for a new wave of mass unrest Monday as anti-government demonstrators blocked major roads to "shut down" Bangkok in a bid to thwart February elections and overthrow the nation's democratically elected prime minister.

The intensified protests, which could last weeks or more, raise the stakes in a long-running crisis that has killed at least eight people in the last two months and fuelled fears of more bloodshed to come and a possible army coup.

Overnight, an unidentified gunman opened fire on protesters camped near a vast government complex, shooting one man in the neck who was admitted to a nearby hospital, according to the city's emergency medical services.

In a separate incident elsewhere, another gunman fired about 10 shots at the headquarters of the headquarters of the opposition Democrat Party, shattering several windows but causing no casualties, said Police Major Nartnarit Rattanaburi.

The protesters are demanding Yingluck's administration be replaced by a non-elected "people's council" which would implement reforms they say are needed to end corruption and money politics. Critics have lashed out at the moves as a power struggle aimed at bringing the Southeast Asian nation's fragile democracy to a halt. Candlelight vigils have been held in the city to counter the shut down and urge the Feb. 2 election to be held on schedule despite an opposition boycott.

In a speech late Sunday, protest leader Suthep Thaugsuban repeated a vow that neither he nor his supporters will negotiate an end to the crisis.

"In this fight, defeat is defeat and victory is victory. There is no tie," he said. "The masses from all walks of life have woken up. They're aware that we are the owners of Thailand."

Demonstrators set up stands in the middle of several major intersections Bangkok and were forcing drivers to turn their cars around. At one, protesters had hung huge Thai flags from an overhead walkway. Bangkok has a subway system and an overheard train system, and traffic was noticeably heavier on both.

Protesters have vowed to surround Cabinet ministries to prevent them from functioning, and vowed to cut water and electricity to the private residences of Prime Minister Yingluck Shinawatra and her Cabinet.

The crisis dates back to 2006, when mass protests calling for then-Prime Minister Thaksin Shinawatra — Yingluck's brother — to step down because of alleged corruption and abuse of power led to a military coup. Since then, supporters and opponents of Thaksin have vied for power, sometimes violently.

The protesters say that billionaire Thaksin, who lives in exile, continues to manipulate Thai politics. Thaksin commands overwhelming support in Thailand's less well-off rural areas, where voters are grateful for his populist programs, including virtually free health care. He and his allies have won every national election since 2001.

Since Yingluck assumed the premiership after 2011 elections, she has walked a careful tightrope with the army and her opponents that succeeded in maintaining political calm. But the trigger for the latest protests was an ill-advised move late last year by ruling party lawmakers to push through a bill under the guise of a reconciliation measure offering a legal amnesty for political offenders. The last-minute inclusion of Thaksin led to public outrage and the bill was voted down.

Since then, demonstrators have steadily escalated pressure on Yingluck, attacking her office at government house and the city's police headquarters with slingshots and homemade rocket launchers, and occupying the compounds of several government agencies they withdrew from last month.

There are fears the protesters are trying to incite violence to prompt the military to intervene, and Yingluck has dealt softly with demonstrators in a bid to keep the situation calm. Concern about a coup is high because of the army's history of intervening in politics.

The powerful army commander General Prayuth Chan-ocha has repeatedly said he does not want his forces drawn into the conflict; but in a sign of apparent impatience late last month, he refused to rule out the possibility of a military takeover.

The grass-roots pro-Thaksin Red Shirt movement, closely allied to Yingluck's Pheu Thai Party, has said it will mobilise its supporters to fight any coup.

Most Bangkok residents, however, have more practical concerns. The U.S. Embassy has urged its citizens to stock up essential items like food and water — enough to last two weeks. There were signs hoarding had begun with bread already sold out at some supermarkets. Thai authorities have dismissed the American advice as overly cautious.

Protest leaders have said they will maintain their "shutdown" of Bangkok for weeks, or until they obtain their goal. Their recent demonstrations have drawn up to 150,000-200,000 people at their height.

The protesters' attempt to destabilise the country has been assisted by the opposition Democrat Party, which is boycotting the February elections. The main protest leader is a former senior Democrat leader, Suthep Thaugsuban, who served at deputy prime minister in the party's 2008-2011 government.

In 2010, Suthep ordered the army to crack down on Red Shirt protesters backing Thaksin who occupied downtown Bangkok for two months. Those protests ended with 90 dead, mostly protesters.

Another deputy prime minister, Surapong Tovichakchaikul, said a combined force of around 12,000 police officers and 8,000 soldiers was being deployed to maintain order in Bangkok.